Investigating factors that could affect milk production of cows is an important way to improve the
efficiency of production systems. The purpose of this study was to verify and quantify the influence
of calf sex on milk production and lactation length in herds of Holstein, Gir, and Guzera cows. Data
from 10,780 lactations of 4,807 Holstein cows that calved between 2001 and 2013; 18,898 lactations
of 13,172 Gir cows that calved between 1985 and 2013; and 5,277 lactations of 3,972 Guzera cows
that calved between 1987 and 2013 were used. Both the accumulated 305-day milk yield (P305) and
the length of the lactation period up to 305 days (DL305) were evaluated. Analysis of variance was
performed by the least squares method using the GLM procedure in the SAS statistical program. The
P305 was not influenced by the sex of the calf in the Holstein breed. However in the zebu breeds (Gir
and Guzera), both P305 and DL305 were significantly affected (P < 0.01) by the sex of the calf, with
higher production and average length of lactation in cows that calved males. In addition, a significant
difference was also nested within sex of calf and age at first calving (P < 0.05) in the Gir breed. The
results indicate that for the zebu breeds, calf sex influences production characteristics.